It’s a common criticism of wind and solar power from the anti-renewables crowd: Using these common renewable energy sources doesn’t really lead to greenhouse gas emission reductions – and is prohibitively expensive – because coal and natural gas plants have to ramp up and down frequently in response to their variable production.
Well it’s not true. So says the National Renewable Energy Laboratory in one of the key findings of its ongoing Western Wind and Solar Integration Study. Sure, there are some downsides to “cycling,” the lab found, but they are so tiny compared to the benefits gained by fueling electrical generation with free wind and sun, that they barely rate as a footnote.
“The negative impact of cycling on overall plant emissions is relatively small,” the researchers reported. “The increase in plant emissions from cycling to accommodate variable renewables are more than offset by the overall reduction in CO2, NOx, and SO2. In the high wind and solar scenario, net carbon emissions were reduced by one third.”
Likewise with costs. There were some added “cycling costs” when renewables on the grid rose, but they were on the order of 2 to 5 percent, even with as much as one-third renewables on the grid. Or to put it another way, while the extensive use of renewable energy results in an additional $35 million to $157 million in cycling costs, we’d be saving $7 billion in fuel costs.
One more key finding highlighted by the NREL in its 2020 scenario for 13 Western states:
Wind and solar impact gas and coal plants very differently. Adding 4 megawatt-hours of renewable generation displaces 1 MWh of coal generation and 3 MWh of gas. Wind tends to reduce generation from combustion gas turbines, while solar tends to increase starts and ramps of gas turbines to meet peaks that occur at sunset. The most significant cycling impact from increased wind and solar is the increased ramping of coal plants.
In the first phase of the integration study, the NREL had found that integration of 35 percent wind and solar could be accomplished with surprisingly little new infrastructure, if good solar and wind forecasting and demand-response programs were adopted. The lab said that “a 35% penetration of solar and wind power would reduce fuel costs by 40% and carbon emissions by 25%–45%—the rough equivalent of taking 22–36 million cars off the road.”